OK Now I have a problem with my
-WaterFurnace NDV038111CTL
-Vertical loop

-DHW Setup is a single 80 gallon electric water heater.

Went to wash my hands and got scalded!

-WF unit is in heating mode.
-DSH turned "OFF"  If I turn the switch on the DSW High Limit light comes on and stays on.
-DSH Out water line too hot to touch
-DSH pump seemed to be "not running" but too hot to touch.
-I disconnected the blue wire from the DSH Pump relay (CR1 NO terminal)
        Same issue.
-I dosconnected the pink wire fron the L2 Fused connection. There is absolutely no way the pump is getting power. Both wires (pink and blue) were traced all the way to controller board and are disconnected.

Water Temp on the DHS Out line is 164 degrees!

Noticed the WF has been running "almost" non-stop today.

ETW = 66.1 degrees
LWT = 65.8 Degrees

Loop in = 46.5 psi
Loop out = 42.0 psi

Something is "Pushing" the domestic water through the DHW pump. 

- Air entering return is 74.2 degrees
- Air leaving blower is 77.1 degrees
- This time I checked and all registers are fully open.

This is baffling me. What could possibly be pushing domestic water through the DSH system? It sure is not the DSH Pump!

Thanks in advance for any advice you might have. I'm afraid to shut off the ball valves in the DSH loop at the WH because I've no idea if that will cause more problems. 

Thanks!

John

why are u sure the dsh has overheated the water and not the water heater?
joe

More info:
With the WaterFurnace unit turned off, we ran hot water downt he tub until the temp dropped from 163 down to 131. I turned the WF unit back on, but this time with the ball valves shut - isolating the water heater from the WF DSH. Now the air temps are:
- Entering the return = 74.8
- at the registers = 81.9

-The DSH pump and plumbing has cooled down.

This is more typical of the heating performance in the past.

Any idea what might be making water flow through the DSH system when the pump is disconnected from power?

What kind of damage might have (or might) occur because of this?

Thanks!
John

Joe - That's a good question and, I must admit, I feel a few watts short of bright right now...

However: When the WF unit was turned off for about 30-45 minutes, the temps on the DSH pump and plumbing inside the cabinet dropped significantly. As soon as I turned the unit back on, the temps came right back up. And that is with both wires (pink and blue) for the DSH pump disconnected from power. Something is making water circulate through this system and it's not the pump. There was no one else at home and no water being used in the house.

Do I understand that you have no buffer tank?
How long have you had the heat pump?

Joe - You are correct. No buffer tank. A single 80 gallon electric tank. Unit has been installed for just about two years now.

Three problems in the past:

1. Early on - A channel (zone) on the Intellizone zapped out and (intermittently) would not open the damper. Moved to another zone.

2. Had a bad thermostat. Temp display varied up or down 5-6 degrees when room temp was stable. Replaced it.

3. Had the energy saving features on the thermostats competing with the Intellizone features i.e. compressor lockout and stage two delay.

Those three issues were not so bad and, with exception of the energy saving features config, easily fixed. This one has me stumped because it "looks like" the impossible is happening.

you seem to be of the sort that thinks a buffer tank is required. Please know that my last house also had a WaterFurnace unit (Premier II) with DSH and a single 80 gal tank. Ten years and we had fantastic performance out of that system. This is why I duplicated the setup in the new SIP house. It would be difficult to add a buffer tank now because the utility room was not designed with extra space...

Thanks!
John

I'm a believer that heat migrates (to areas with less heat) and have a situation where a water heaters electric consumption went up for DHW without a buffer, but was reduced by 50% of historic rates with a buffer tank and DSH.
You have however 2 years of history without the current problem and a zone damper problem as well as a small delta T between entering and leaving air temps.......so make sure your dampers are responding correctly.

J

Joe - I agree that heat moves from more to less until an equilibrium is established. In this case though, how could hea move through the plumbing and raise the temp in the DSH pump that high in just a few minutes?

Recorded measurements:

Before shutting off plumbing valve to water tank:
- Loop Water in = 66.1 degress and Water out =65.8 (small Delta T)
- Air Entering = 74.2 and Air leaving = 77.1 (small Delta T)
- DHW a blistering 164 degrees!
- DHW pump not running/disconnected from power.
- WF unit ran almost continuously throughout the day

After shutting plumbing valve between DSH and water heater tank:
- Loop water in = 67.3 and Water out = 66.8 (a little better)
- Air entering = 74.8 and Air leaving = 82.7 out MUCH BETTER!
- DSH connected back to power, turned off by switch and not running
- WF is running for short periods. Off more than on.

The system seems to be running great now, but the dsh plumbing is shut off. Tomorrow when I can see straight again, I'll open the plumbing up and monitor again.

Is there any mechanism that can make water flow through the DSH system when 1. Pump not under power. 2. No water being used int he house. ? Stumped here.... Going to make a rum and coke...

John

Not sure what is going on with the DSH. 

There are a couple of other things   that caught my eye.

“- Loop water in = 67.3 and Water out = 66.8 (a little better)
- Air entering = 74.8 and Air leaving = 82.7 out MUCH BETTER!”

Both of these should be more of a delta.

Most systems that I have installed have at least a 20° rise in air temp and at least a 5° drop in water temp.

Dewayne - I agree. Before cutting off the water heater tank, the heat transfer was water to water. Now the transfer is water to air. But you're right, something still seems off.

One detail I forgot to put in previously: There is a component inside the unit that is wrapped with thin black foam insulation. It is a cylindrical shape about 4 inches in diameter and 5 inches long. There is a tube welded to each end. This "can" shaped thing had frost on it coming out from beneath the insulation. If a gun was pointed at me and had to guess... And at the risk of being laughed at, I'd say it is a "suction line filter/dryer". There also was frost on the tube that goes from the reversing valve to the heat exchanger near the heat exchanger and at the point where the DHW "in" pipe joins it. This thing had frost on it when the dhw was 164 degrees. Since cutting the plumbing off, the frost melted and is no more. That must be important an important detail and maybe telling of the problem? Following the diagnostic procedures, I did energize the reversing valve manually and heard a solid click.

If I have to get a service guy in, so be it. I really want to understand how my system works. I promote GeoThermal as part of the energy efficient "package" in my SIP homes.

Thanks again for your help!

john

I also have an NDV038 connected to an 80 gallon water tank, though it is a buffer, and about the highest temp I've ever seen in the buffer is 115 or so, summer or winter.

I agree that John's air and water temps are odd and I agree with Dewayne as to normal Delta Ts

I would note that DSH pumps when running become quite hot even if the water they are moving isn't really hot. If the pump isn't running but its plumbing has very hot water then the pump would warm by conduction.

It makes sense that the DSH limit would be active since it interlocks the pump at 135 entering (domestic water) temp.

If the WF and the water heater are fairly close to each other and at roughly the same elevation, natural convection could drive water through the DSH and back into the tank. I'd be curious to know if the plumbing arrangement would support natural convection and how much water had to be drawn off to drop the temp from 160 to 130. I'd also like to know the immediately previous history of hot water use prior to the scalding incident...very little over the previous several hours? If the drawdown required was much less than the tank volume that supports my theory that natural convection created a small pocket of very hot water at the top of the tank.

There are a couple of additional clues:

1) Near continuous WF operation - unit is having trouble meeting load.

2) low delta-Ts, water and air - WF is not transferring anywhere near the amount of heat it would in normal operation

I therefore theorize that either the WF has lost a significant portion (half or more) of its refrigerant charge or something has gone wrong with its TXV. In either event, the evaporator (loop water coax during heating season) would be starved of liquid refrigerant and return very high superheat to the compressor. The compressor would add its usual additional superheat, and possibly quite a bit more superheat since low refrigerant flow would starve it of cooling.

The DSH is first in line to get refrigerant from the compressor discharge. Extraordinarily high superheat would result in the DSH seeing very very hot refrigerant, perhaps 200 or higher, and that could allow it to heat some water to 160, as long as the water wasn't flowing fast, as would be the case in a natural (pump off) rather than forced convection scenario.

I'm far from certain that my theory is correct - I'm way out on a limb with several assumptions based on scanty information.

Another option is that something has happened to dramatically reduce airflow. The prior damper issue supports that hypothesis a bit. Very low condenser airflow would raise head pressure and temperature and shift additional heat rejection to the DSH. However, under normal refrigerant flow, superheat and charge conditions, compressor discharge hot enough to make 160+ DSH water would be accompanied by such high pressures and currents that I would expect the compressor to trip out on high discharge pressure or internal overload. Additionally, greatly reduced airflow would drive up airside Delta T, which John has not reported, though I don't know where he is taking air temp measurements. A stuck damper would cause the ECM to try very hard to overcome the restriction by increasing speed, and that would be accompanied by abnormal blower noise, and John seems observant enough to have reported that if it was occurring.

I'm very much looking forward to more info on this one.

BTW, no harm should come from valving out the DSH so long as the DSH pump is disabled.

I would concur with the above post. what needs to be looked at next is the pressures in the compressor loop. do they match the specified pressure to temperature charts for the equipment. if not then you need to look at what might be affecting the compressor and the freon cycle. could be a clogged heat exchanger on either side of the unit, as geothermal systems rely on heat exchangers for proper operation. just a thought. Mars

Engineer - Thank you for your input. You might be on to something with the refrigerant possibly being low. I do not have the equipment or know-how to check refrigerant levels. Read about the evaporator coil freezing up in the summer below.

To answer some questions:

- The dampers are open and all registers are wide open. I learned that lesson twice last year when: 1. Someone closed all registers upstairs (loud blower noise). and 2. Zone one on the Intellizone was intermittently not opening it's damper when supposed to. I moved the damper and config to zone 4. Those two problems are solved. it does not seem that there is a restricted airflow problem. OH yeah: Zone two is downstairs set at Comfort and 70%. Zone 4 is upstairs set at Comfort and 45%

- Locations where air temps were measured:
a. Entering - at the return grill external to the air filter. BTW Air Filter is clean.
b. Leaving - Through a small hole in the rubber boot between the top of the WF unit and the distribution box that has the dampers mounted on top of it. This is just above the aux heat strips.

- Another important tid-bit I left out: During the summer the evaporator coil was freezing up. There was a tremendous amount of humidity this summer. The solution(?) was found to be two-fold. Turned off the dehumidifier feature (Intellizone SW6-4) and increased the blower speeds. It seemed to help but periodically some frost would show up at the very top and the very bottom of the evaporator coil. Having the dehumid feature turned on seemed to make the icing problem worse. Currently the bower speed dip switches are set to: 1 - 650, 3 - 850, 4 - 1000, 7 - 1300, 8 - 1400. In cooling mode it ran at 1000 cfm much of the time. Now, in heating mode, it is running the same 1000 cfm.

Currently - The unit woke me up by running constantly again. It has been on solid for about three hours that I know of. There is frost on the dryer/filter (can) thing again..

The structure is a 2 story 1700 sf SIP house located in East Alabama. The first and second floors are hard to differentiate in zoning because the vaulted living room, loft and upper hallway are all one big airspace. Upstairs has two bedrooms a loft and one bath. I believe the ducting upstairs is inadequate to support the airflow when it is the only active zone (usually in summer/cooling mode). To help that situation I set the downstairs damper to not fully close by adjusting the damper stop set screw. When the upstairs zone is open, a good bit of air is allowed past the downstairs damper. There does not appear to be an issue with airflow since making that adjustment. That was done early on just after installation. I can't blame the installer too much because this was his first GeoThermal install and I approached him to help. He had never seen a SIP home before nor did he have experience with GeoThermal. There was only one GeoTherm HVAC company in the area at the time of this install, and his price reflected it. The owner was WAY to proud of his work. and wanted over $30K (double what it cost to install). BTW. The house has a HERS Rating of 49. So in fairness, my HVAC guy is not to blame.. It was an experiment for each of us and I knew that from the start.

- We have ceiling fans throughout. In heating mode downstairs is set to 76. (we like it warm). The upstairs thermostat is set for 73 and stays at 74/75. I've not seen the upstairs zone call for heat as of yet. I have adjusted the thermostat upstairs higher to be sure it does call for heat. It does.

- The 80 gal water heater is sitting right next to the WF unit. The idea of natural convection is plausible. Yesterday there were were two adults who took showers before leaving to shop. But now, there has been no water usage for at least 6 hours and the water heater is valved off from the DSH... I don't think that was it because my wife thinks it has been running like this for several days. Maybe even since the cold wave came.

- I can see light through all areas of the condenser and the filter is brand new.

- My last house had a WF w/DHW and 80 gal tank. No buffer tank. In the summer the water temp was 135 most all the time. The breaker to the water heater was turned off when warm weather came.

My gut feeling is that there is something wrong in the heat exchanger. If I turn on the dsh and open the plumbing, the focus of btu's goes to the dhw and not to the air. It seems backwards. However, the unit is not putting a whole lot of btu's int he air and the dsh is turned off. It's almost like the evaporator coil is not getting hot enough..

OK well.. That was a lot of info. Thanks for reading so much and helping me.

John

One more thing just noticed. The evaporator coil is warm only in the very center (from top to bottom). Unscientific measurement but it is obvious that the top and bottom of the coil are cool. No higher than room temperature. It's funny that the center is cool because in the summer, in cooling mode, the center was warmer and the top and bottom was freezing up. Gut feeling tells me this is the clue to zoom in on. And I bet, it has something to do with what Engineer said about low refrigerant....

John

I'm surprised a 1700 SF SIP house requires an 038. Was a proper load calc done to justify the unit selection? That superb HERS rating further suggests oversized. Long term if you could trade for an 026 you might be way better off. That's based on scanty internet info - I don't know your glass info (windows + doors) which can have a huge impact. Is that 1700 SF total or each floor?

Evap icing may be caused by low ref. charge, though a TXV will insulate the unit from low charge to some extent. It may have masked a very slow leak for a year or so.

What are your thermostat setpoints in summer? We set at 77 and discharge air is >50 even with Intellizone dehu selected (cuts airflow 15%) I like it dry, <50% RH.

Too low a Tstat setting, <68 can cause icing, depending on airflow.

The variable temperature across the heat exchanger may also be caused by low charge. Look closely at how refrigerant enters the heat exchanger - it does so at several points, and the tubes nearest the points of entry may be the only ones condensing gas.

If you are competent and safe to work around exposed high AC voltage, I'd like to know unit or compressor amps. You'd need to have or borrow an AC clamp meter. That's less intrusive than checking refrigerant pressure. Low amps would indicate low charge, high amps would indicate a restriction bottling refrigerant up in the DSH.

Engineer - Thanks for the ideas. Yeah. I have a manual J (can send it to ya to review). We did not know there was a smaller unit then the 38.... Also, I made a change during construction to change the attic space above the master BR into a loft. That added approx 200 sf and more volume in the "vaulted" area. So we figured the 3 ton would not be too much over kill. The Manual J called for 2.1 tons. The total sf of the house, upstairs and down, is approx 1700 sf. It does however have a HUGE vaulted area about 22 ft high and 38 ft wide. The windows are Pella Series 10 ThermaStar windows. At the time they were the highest performing windows available in my area. Low-E and Argon gas. Energy Star award winners they were. Doors are Energy Star rated as well.

In the summer we keep the thermostat set at 73-74.

If a 026 would be better for my house, I would gladly trade out.

OK. After studying the layout of refrigerant and water plumbing, I've come to the conclusion that the reversing valve is the traffic cop in this maze of pipe. The compressor has two lines, a thin(er) uninsulated copper line that goes to the rear of the heat exchanger, and a thick(er) insulated copper line that goes into the reversing valve. A line from the reversing valve goes up to the evaporator coil. Coming down from the evap coil is a line that connects to the thing (filter/dryer?) that is freezing. From there the line goes into the heat exchanger. The closer it gets to the heat exchanger, the more frost/freezing there is. It looks like it joins up with the DHW "IN" line right as it goes into the exchanger. (There must be an acronym for heat exchanger.)

I ain't skeert of no high voltages and don't need no insulatin tools neither! hahaha Seriously, I've been around electricity all my life. Was zapped in the AF by 48 volts and a zillion amps on a teletype/telephone battery cross connect frame. That one left a mark. Learned the lessons well, although there were too many lessons...

Trying to attach a few pics of the frozen parts... See if this works... Then, I'm calling a friend who owns a HVAC company. Maybe he can come over and measure the refrigerant.. Then off to borrow or purchase an amp clamp.

You all are very kind and patient. Thank you!

John

Here is a diagram that might help

Maybe this will be better

OK now... This is great except, my unit has but one coax coil. I suspect the two shown in the diagram are actually melded together in one assembly? It would fit because of the number of connections I see.

Holy cow I see how this works! So it looks like what I've been referring to as the evaporator coil is actually called an air coil.. Sorry about that.

I received and reviewed your load calc. My initial take is that an 026, 2.25 tons nominal would be a much better fit, though I'd have to know your loop field deign operating conditions to be sure. That review falls under ACCA Manual S wherein we figure out what a particular unit's capacity should be under conditions custom to the specific application. It is rarely acceptable to take the manual J load, divide by 12k and buy a unit based on that.

Your heat load (27kbtuh) exceeds your cool load by a half ton. I think an 026 would still hack it, but addition of a 5 kw heat strip would be cheap insurance since you say you like to be warmer.

Handy diagram. That icing seems to lend credence to my low charge or bum TXV hypothesis. Suction side is way too cold, and that suggests too low refrigerant pressure. That could be caused by very low water flow or very cold water on the loop side, but your notes don't support that. I'll cheerfully admit to NOT being a veteran tech. I'm long on theory, not so much hands on, so there may be something basic I'm missing.

I'm 99 44/100 % sure your HVAC guy owns a clamp ampmeter. If he's any good he'll resolve your issue quickly - no reason he can't swap a bum TXV or fix a leak and recharge if needed. Docs on WF site give details of expected pressures and amps. The waterside might scare him off, though...